Cryptic and free skin irritants of the daphnane and tigliane types in latex of Excoecaria agallocha

• Published in: Planta medica Vol. 60; no. 4; p. 351
• Main Authors: Karalai, C, Wiriyachitra, P, Opferkuch, H.J, Hecker, E. (Prince of Songkla Univ., Hat-Yai (Thailand). Faculty of Science. Dept. of Chemistry)
• Format: Journal Article
• Language: English
• Published: Germany 01.08.1994
• Subjects: Animals; ENFERMEDADES DE LA PIEL; ESTER; ESTERES; Esterification; EUPHORBIACEAE; Irritants - chemistry; Irritants - toxicity; LATEX; Latex - chemistry; Latex - toxicity; MALADIE DE LA PEAU; Mice; Molecular Structure; Plant Extracts - chemistry; Plant Extracts - toxicity; Skin - drug effects
• ISSN: 0032-0943; 1439-0221
• DOI: 10.1055/s-2006-959499

In the extremely skin irritant and caustic latex of Excoecaria agallocha the major part of the polyfunctional diterpene esters (DTE) (group 1) are aliphatic polyunsaturated 9,13,14-orthoesters of the daphnane-type parent alcohol 5beta-hydroxyresiniferonol-6alpha, 7alpha-epoxide, esterified simultaneously in their 20-positions with aliphatic saturated homologous n-carboxylic acids (even numbered, C22- C30). The minor part of DTE is composed of analogous structures of 5beta, 12beta-dihydroxyresiniferonol-6alpha, 7alpha-epoxide (group 2) and of aliphatic 13-polyunsaturated, 20-saturated diesters of the tigliane-type parent alcohol 12-deoxyphorbol (group 3). All three groups of DTE exhibit practically no irritant activity on the mouse ear. By alkaline transesterification of groups 1-3, the corresponding highly irritant multicomponent mixtures of Excoecaria factors A (OH-20 deacylated) are released. They comprise a mixture of the known Excoecaria factors A1/A2/A3 and three mixtures of hitherto unknown Excoecaria factors A4/A5, A6/A7 and A8/A9. The groups 1-3 are typical structures of "cryptic irritants". By an alternative, extremely mild separation procedure the highly irritant mixture A1/A2/A3 was obtained directly. It represents the "free" Excoecaria factors, the natural constituents of the latex responsible for its bioactivity.